Commit | Line | Data |
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39ec58f3 LB |
1 | /* |
2 | * linux/arch/arm/lib/uaccess_with_memcpy.c | |
3 | * | |
4 | * Written by: Lennert Buytenhek and Nicolas Pitre | |
5 | * Copyright (C) 2009 Marvell Semiconductor | |
6 | * | |
7 | * This program is free software; you can redistribute it and/or modify | |
8 | * it under the terms of the GNU General Public License version 2 as | |
9 | * published by the Free Software Foundation. | |
10 | */ | |
11 | ||
12 | #include <linux/kernel.h> | |
13 | #include <linux/ctype.h> | |
14 | #include <linux/uaccess.h> | |
15 | #include <linux/rwsem.h> | |
16 | #include <linux/mm.h> | |
17 | #include <linux/sched.h> | |
18 | #include <linux/hardirq.h> /* for in_atomic() */ | |
5a0e3ad6 | 19 | #include <linux/gfp.h> |
7816e210 | 20 | #include <linux/highmem.h> |
a3a9ea65 | 21 | #include <linux/hugetlb.h> |
39ec58f3 LB |
22 | #include <asm/current.h> |
23 | #include <asm/page.h> | |
24 | ||
25 | static int | |
26 | pin_page_for_write(const void __user *_addr, pte_t **ptep, spinlock_t **ptlp) | |
27 | { | |
28 | unsigned long addr = (unsigned long)_addr; | |
29 | pgd_t *pgd; | |
30 | pmd_t *pmd; | |
31 | pte_t *pte; | |
516295e5 | 32 | pud_t *pud; |
39ec58f3 LB |
33 | spinlock_t *ptl; |
34 | ||
35 | pgd = pgd_offset(current->mm, addr); | |
36 | if (unlikely(pgd_none(*pgd) || pgd_bad(*pgd))) | |
37 | return 0; | |
38 | ||
516295e5 RK |
39 | pud = pud_offset(pgd, addr); |
40 | if (unlikely(pud_none(*pud) || pud_bad(*pud))) | |
41 | return 0; | |
42 | ||
43 | pmd = pmd_offset(pud, addr); | |
a3a9ea65 SC |
44 | if (unlikely(pmd_none(*pmd))) |
45 | return 0; | |
46 | ||
47 | /* | |
48 | * A pmd can be bad if it refers to a HugeTLB or THP page. | |
49 | * | |
50 | * Both THP and HugeTLB pages have the same pmd layout | |
51 | * and should not be manipulated by the pte functions. | |
52 | * | |
53 | * Lock the page table for the destination and check | |
54 | * to see that it's still huge and whether or not we will | |
55 | * need to fault on write, or if we have a splitting THP. | |
56 | */ | |
57 | if (unlikely(pmd_thp_or_huge(*pmd))) { | |
58 | ptl = ¤t->mm->page_table_lock; | |
59 | spin_lock(ptl); | |
60 | if (unlikely(!pmd_thp_or_huge(*pmd) | |
61 | || pmd_hugewillfault(*pmd) | |
62 | || pmd_trans_splitting(*pmd))) { | |
63 | spin_unlock(ptl); | |
64 | return 0; | |
65 | } | |
66 | ||
67 | *ptep = NULL; | |
68 | *ptlp = ptl; | |
69 | return 1; | |
70 | } | |
71 | ||
72 | if (unlikely(pmd_bad(*pmd))) | |
39ec58f3 LB |
73 | return 0; |
74 | ||
75 | pte = pte_offset_map_lock(current->mm, pmd, addr, &ptl); | |
76 | if (unlikely(!pte_present(*pte) || !pte_young(*pte) || | |
77 | !pte_write(*pte) || !pte_dirty(*pte))) { | |
78 | pte_unmap_unlock(pte, ptl); | |
79 | return 0; | |
80 | } | |
81 | ||
82 | *ptep = pte; | |
83 | *ptlp = ptl; | |
84 | ||
85 | return 1; | |
86 | } | |
87 | ||
cb9dc92c NP |
88 | static unsigned long noinline |
89 | __copy_to_user_memcpy(void __user *to, const void *from, unsigned long n) | |
39ec58f3 LB |
90 | { |
91 | int atomic; | |
92 | ||
39ec58f3 LB |
93 | if (unlikely(segment_eq(get_fs(), KERNEL_DS))) { |
94 | memcpy((void *)to, from, n); | |
95 | return 0; | |
96 | } | |
97 | ||
98 | /* the mmap semaphore is taken only if not in an atomic context */ | |
99 | atomic = in_atomic(); | |
100 | ||
101 | if (!atomic) | |
102 | down_read(¤t->mm->mmap_sem); | |
103 | while (n) { | |
104 | pte_t *pte; | |
105 | spinlock_t *ptl; | |
106 | int tocopy; | |
107 | ||
108 | while (!pin_page_for_write(to, &pte, &ptl)) { | |
109 | if (!atomic) | |
110 | up_read(¤t->mm->mmap_sem); | |
111 | if (__put_user(0, (char __user *)to)) | |
112 | goto out; | |
113 | if (!atomic) | |
114 | down_read(¤t->mm->mmap_sem); | |
115 | } | |
116 | ||
117 | tocopy = (~(unsigned long)to & ~PAGE_MASK) + 1; | |
118 | if (tocopy > n) | |
119 | tocopy = n; | |
120 | ||
121 | memcpy((void *)to, from, tocopy); | |
122 | to += tocopy; | |
123 | from += tocopy; | |
124 | n -= tocopy; | |
125 | ||
a3a9ea65 SC |
126 | if (pte) |
127 | pte_unmap_unlock(pte, ptl); | |
128 | else | |
129 | spin_unlock(ptl); | |
39ec58f3 LB |
130 | } |
131 | if (!atomic) | |
132 | up_read(¤t->mm->mmap_sem); | |
133 | ||
134 | out: | |
135 | return n; | |
136 | } | |
137 | ||
cb9dc92c NP |
138 | unsigned long |
139 | __copy_to_user(void __user *to, const void *from, unsigned long n) | |
140 | { | |
141 | /* | |
142 | * This test is stubbed out of the main function above to keep | |
143 | * the overhead for small copies low by avoiding a large | |
144 | * register dump on the stack just to reload them right away. | |
145 | * With frame pointer disabled, tail call optimization kicks in | |
146 | * as well making this test almost invisible. | |
147 | */ | |
c626e3f5 | 148 | if (n < 64) |
cb9dc92c NP |
149 | return __copy_to_user_std(to, from, n); |
150 | return __copy_to_user_memcpy(to, from, n); | |
151 | } | |
152 | ||
153 | static unsigned long noinline | |
154 | __clear_user_memset(void __user *addr, unsigned long n) | |
39ec58f3 | 155 | { |
39ec58f3 LB |
156 | if (unlikely(segment_eq(get_fs(), KERNEL_DS))) { |
157 | memset((void *)addr, 0, n); | |
158 | return 0; | |
159 | } | |
160 | ||
161 | down_read(¤t->mm->mmap_sem); | |
162 | while (n) { | |
163 | pte_t *pte; | |
164 | spinlock_t *ptl; | |
165 | int tocopy; | |
166 | ||
167 | while (!pin_page_for_write(addr, &pte, &ptl)) { | |
168 | up_read(¤t->mm->mmap_sem); | |
169 | if (__put_user(0, (char __user *)addr)) | |
170 | goto out; | |
171 | down_read(¤t->mm->mmap_sem); | |
172 | } | |
173 | ||
174 | tocopy = (~(unsigned long)addr & ~PAGE_MASK) + 1; | |
175 | if (tocopy > n) | |
176 | tocopy = n; | |
177 | ||
178 | memset((void *)addr, 0, tocopy); | |
179 | addr += tocopy; | |
180 | n -= tocopy; | |
181 | ||
a3a9ea65 SC |
182 | if (pte) |
183 | pte_unmap_unlock(pte, ptl); | |
184 | else | |
185 | spin_unlock(ptl); | |
39ec58f3 LB |
186 | } |
187 | up_read(¤t->mm->mmap_sem); | |
188 | ||
189 | out: | |
190 | return n; | |
191 | } | |
cb9dc92c NP |
192 | |
193 | unsigned long __clear_user(void __user *addr, unsigned long n) | |
194 | { | |
195 | /* See rational for this in __copy_to_user() above. */ | |
c626e3f5 | 196 | if (n < 64) |
cb9dc92c NP |
197 | return __clear_user_std(addr, n); |
198 | return __clear_user_memset(addr, n); | |
199 | } | |
c626e3f5 NP |
200 | |
201 | #if 0 | |
202 | ||
203 | /* | |
204 | * This code is disabled by default, but kept around in case the chosen | |
205 | * thresholds need to be revalidated. Some overhead (small but still) | |
206 | * would be implied by a runtime determined variable threshold, and | |
207 | * so far the measurement on concerned targets didn't show a worthwhile | |
208 | * variation. | |
209 | * | |
210 | * Note that a fairly precise sched_clock() implementation is needed | |
211 | * for results to make some sense. | |
212 | */ | |
213 | ||
214 | #include <linux/vmalloc.h> | |
215 | ||
216 | static int __init test_size_treshold(void) | |
217 | { | |
218 | struct page *src_page, *dst_page; | |
219 | void *user_ptr, *kernel_ptr; | |
220 | unsigned long long t0, t1, t2; | |
221 | int size, ret; | |
222 | ||
223 | ret = -ENOMEM; | |
224 | src_page = alloc_page(GFP_KERNEL); | |
225 | if (!src_page) | |
226 | goto no_src; | |
227 | dst_page = alloc_page(GFP_KERNEL); | |
228 | if (!dst_page) | |
229 | goto no_dst; | |
230 | kernel_ptr = page_address(src_page); | |
231 | user_ptr = vmap(&dst_page, 1, VM_IOREMAP, __pgprot(__P010)); | |
232 | if (!user_ptr) | |
233 | goto no_vmap; | |
234 | ||
235 | /* warm up the src page dcache */ | |
236 | ret = __copy_to_user_memcpy(user_ptr, kernel_ptr, PAGE_SIZE); | |
237 | ||
238 | for (size = PAGE_SIZE; size >= 4; size /= 2) { | |
239 | t0 = sched_clock(); | |
240 | ret |= __copy_to_user_memcpy(user_ptr, kernel_ptr, size); | |
241 | t1 = sched_clock(); | |
242 | ret |= __copy_to_user_std(user_ptr, kernel_ptr, size); | |
243 | t2 = sched_clock(); | |
244 | printk("copy_to_user: %d %llu %llu\n", size, t1 - t0, t2 - t1); | |
245 | } | |
246 | ||
247 | for (size = PAGE_SIZE; size >= 4; size /= 2) { | |
248 | t0 = sched_clock(); | |
249 | ret |= __clear_user_memset(user_ptr, size); | |
250 | t1 = sched_clock(); | |
251 | ret |= __clear_user_std(user_ptr, size); | |
252 | t2 = sched_clock(); | |
253 | printk("clear_user: %d %llu %llu\n", size, t1 - t0, t2 - t1); | |
254 | } | |
255 | ||
256 | if (ret) | |
257 | ret = -EFAULT; | |
258 | ||
259 | vunmap(user_ptr); | |
260 | no_vmap: | |
261 | put_page(dst_page); | |
262 | no_dst: | |
263 | put_page(src_page); | |
264 | no_src: | |
265 | return ret; | |
266 | } | |
267 | ||
268 | subsys_initcall(test_size_treshold); | |
269 | ||
270 | #endif |